Device for controlling the fuel supply with propeller turbojet engines for aircraft by means of a throttle lever and a trimming lever

ABSTRACT

A plurality of input signals are fed to a computer which determines a &#39;&#39;&#39;&#39;set&#39;&#39;&#39;&#39; signal indicative of a desirable turbine gas temperature of the turbojet engine. The input signals include information as to the engine speed and the air pressure at the altitude at which the engine is operating. An &#39;&#39;&#39;&#39;actual&#39;&#39;&#39;&#39; signal is derived indicative of the existing turbine gas temperature and is compared with the &#39;&#39;&#39;&#39;set&#39;&#39;&#39;&#39; signal to produce an error signal. From the error signal indications are given to the pilot as to the movement required of the trimming lever to achieve the desirable turbine gas temperature for the conditions under which the engine is operating. The error signal can be used for automatic correction of the setting of the trimming lever.

United States Patent Bader 5] Mar. 7, 1972 [54] DEVICE FOR CONTROLLINGTHE FUEL SUPPLY WITH PROPELLER TURBOJET ENGINES FOR AIRCRAFT BY MEANS OFA THROTTLE LEVER AND A TRIMMING LEVER [72] Inventor: Gottfried liader,Uberlingen, Bodensee,

Germany Bodenseewerk Geratetechnik GmbIl, U li nd ns s- .qe ma y [22]Filed: Apr. 17, 1970 [21] Appl.No.: 29,489

[73] Assignee:

US. Cl ..235/l50.21, 60/3928 Field of Search ..235/l50.2l; 60/3928 [56]References Cited UNITED STATES PATENTS 3,357,177 12/1967 Cornett..60/39.28

I Po

MI W1 COMPUTER 3,482,396 12/1969 Nelson et a1. ..60/39.28 3,472,02710/1969 Snow et al ..60/39.28 X 3,469,395 9/ 1969 Spitsbergen et a1..60/39.28 2,701,111 2/1955 Schuck ..235/150.2l X

Primary Examiner-Malcolm A. Morrison Assistant Examiner-Edward 1. WiseAttorney-Darbo, Robertson & Vandenburgh [57] ABSTRACT A plurality ofinput signals are fed to a computer which determines a set" signalindicative of a desirable turbine gas temperature of the turbojetengine. The input signals include information as to the engine speed andthe air pressure at the altitude at which the engine is operating. Anactual signal is derived indicative of the existing turbine gastemperature and is compared with the set signal to produce an errorsignal. From the error signal indications are given to the pilot as tothe movement required of the trimming lever to achieve the desirableturbine gas temperature for the conditions under which the engine isoperating. The error signal can be used for automatic correction of thesetting of the trimming lever.

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DEVICE FOR CONTROLLING THE FUEL SUPPLY WITH PROPELLER TURBOJET ENGINESFOR AIRCRAFT BY MEANS OF A THROTTLE LEVER AND A TRIMMING LEVERBACKGROUND AND SUMMARY OF THE INVENTION This invention relates to adevice for controlling or automatically controlling the fuel supply withpropeller turbojet engines for aircraft by means ofa throttle lever anda trimming lever.

Turbo engines are known to comprise an air inlet at the front and behindwhich is a compressor. The compressor causes a compression of theincoming air to a relatively high pressure. The compressed air entersinto one or several combustion chambers into which fuel is injected. Theair-fuel mixture is burned in the combustion chamber, thereby generatingan extremely hot gas mass which is discharged through a turbine and athrust nozzle. The turbine is driven and abstracts part of the energy ofthe gas mass therefrom. The turbine is' coupled to the compressorthrough a connection shaft. In propeller turbojet engines a relativelylarge proportion of the energy of the hot gas mass is converted intomechanical work by the turbine, and the turbine drives a propeller aswell as the compressor. In such jet engines, the first temperature riseof the air takes place in the compressor in which also a pressure riseto a maximum value takes place. In the combustion chamber the pressuredecreases from the maximum value, while the temperature rises to amaximum value which substantially occurs at the entrance of the turbine.In the turbine, the hot gas mass cools off to a certain extent, whereinthe gas performs work. According to the second law of the theory ofheat, the higher the maximum temperature at the entrance of the turbine,the greater the mechanical power output. This temperature is termedturbine gas temperature.

On the one hand, the turbine gas temperature should be as high aspossible for the reasons as described. While on the other hand, theturbine gas temperature should not exceed specific limits in order toavoid the danger of destruction of the engine. The respective optimumvalue for the turbine gas temperature depends on the mode of operation(takeoff, cruising range, no-load cruising, ground run, reversion) andthe engine speed, as well as on the environmental conditions such ascruising altitude, air temperature and air speed.

Two control elements, a throttle lever and a trimming lever are providedfor controlling such a jet engine. Depending on the selected mode ofoperation, the throttle lever is effective to preestablish a speed and aspecific fuel flow which is so adapted that the required power output isachieved, without exceeding the temperature limit values of the turbine.The fuel flow is automatically controlled in that a constantdifferential pressure is maintained at a throttle, the cross-sectionalarea of which can be adjusted by the throttle lever. With a change inthis differential pressure, the stroke of a fuel pump is varied. Thefuel flow is automatically corrected with changes in the air throughputdue to pressure changes at the air entrance, when altitude and speedchange. The trimming lever is effective to correct the fuel flow independence on the air inlet temperature and the altitude, thereby toattain a preestablished value of the turbine gas temperature which inturn depends on the mode of operation, and thus, on the position of thethrottle lever.

Thus, the maximum permissible turbine gas temperature depends on theengine speed as it is preestablished by the throttle lever, as well ason the cruising altitude and the air pressure, respectively. In order toobtain the turbine gas temperature, a specific position of the trimminglever must be selected in dependence on the air temperature. Generally,this position of the trimming lever is derived from tables. Thisdetermination and adjustment of the trimming lever represents aconsiderable strain on the human pilot and involves the danger of error.In the most favorable case such error may lead to the unavailability offull engine performance, and in the most unfavorable case it can resultin a destruction of the engine due to excessive engine temperatures.

It is an object of this invention to simplify this laboriousdetermination of the trimming lever adjustment required for therespective mode of operation and the respective environmental conditionsand provide automation for the same.

The device, according to the invention, is characterized by a computercontrolled by the speed, air pressure or cruising altitude, and may bethe position of the throttle lever or these data and the airtemperature, for determining a setpoint value for the turbine gastemperature of the engine and for the position of the trimming leverdetermining the turbine gas temperature, respectively, a measuringsensor for measuring the actual value of the turbine gas temperature andof the position of the trimming lever, respectively, and a device forgenerating an error signal, if the actual value deviates from thesetpoint value thus calculated.

According to one embodiment of the invention, the turbine gastemperature is directly measured. The setpoint value of the turbine gastemperature established for the respective mode of operation iscalculated automatically by a computer. An error signal is generated inresponse to deviations between the actual value and setpoint value. Thiserror signal can control an automatic lever control or an indicatingdevice. An indicating device could comprise two blinking lamps with onebeing actuated in dependence on the sign of the deviation. When the one,or the other, blinking lamp lights up, the human pilot may cause theerror signal to disappear by manual actuation of the trimming lever.

In another embodiment of the invention, the position of the trimminglever, which position is required for the desired turbine gastemperature, is used as the input to the computer instead of using theturbine gas temperature of the engine as the input. Thus, a measuringsensor measures the actual value of the trimming lever position. Anindication may be initiated accordingly, by an error signal, or anautomatic control may be effected. In addition to the aforesaid data,the computer must be controlled by a signal representing the airtemperature in order to calculate the setpoint value for the position ofthe trimming lever.

The computer may include a function transmitter for forming a firstsignal proportion as a function of engine speed, as well as an addingamplifier for imposition of the said first signal proportion by a secondsignal proportion dependent on the air pressure (or the cruisingaltitude). When calculating a setpoint value for the position of thetrimming lever, the output of the adding amplifier is additionallysupplied to a multiplier element in which a multiplication by an airtemperature signal is effected for forming the trimming lever setpointvalue. The function transmitter may be a network in wellknown mannercomprising a parallel circuit of differently biased diodes, constitutinga double pole, the current-voltage characteristic of which behavesanalogously to a preestablished'(in this case empirically) function. Byway of example, the design of such a function transmitter is describedin the article by Donaubauer, Lucius and Negele Rechenverstarker(calculating amplifier) in the periodical ELEK- TRONIK 1966, volume 8,page 249 et seq.

Moreover, the measurement of the turbine gas temperature as actual valueof the actual value-setpoint value comparison, according to theinvention, makes it possible to provide a limit switch controlled by theactual value of the turbine gas temperature by which, when a maximumpermissible turbine gas temperature is exceeded, a warning signal and/ora command can be initiated for the automatic return of the trimminglever.

To avoid erroneous manipulations in case of failure of any elements ofthe control chain, several parallel channels are provided forcalculating the setpoint values of the turbine gas temperature, theoutput signals of the various channels being supplied to one or severalcomparison devices. The comparison devices initiate an alarm signal incase of deviation of the setpoint values calculated in the variouschannels.

DESCRIPTION OF THE DRAWINGS FIG. I is a schematic diagram illustratingthe principle of one embodiment of the invention;

FIG. 2 illustrates a second embodiment in which the position of thetrimming lever is the regulating variable;

FIG. 3 is a block circuit diagram of a control chain for the cruisingrange;

FIG. 4 is a block circuit diagram of a control chain for the wholeoperating range; 7

FIG. 5 is a block circuit diagram of an embodiment similar to that ofFIG. 3 with the position of the trimming lever as regulating variable;

FIG. 6 illustrates an example of an adapter element applicable to theinvention;

FIG. 7 illustrates an example of a function transmitter applicable tothe invention for copying an empirically determined function;

FIG. 8 illustrates an example of the function approximated by thefunction transmitter of the invention;

FIG. 9 illustrates an example of a calculating element used with theinvention;

FIG. 10 illustrates an example ofa summation element used with theinvention;

FIG. 11 illustrates an example of the electrical valves" used with theinvention, and

FIG. 12 illustrates the characteristic of the electrical valve of FIG.11:

FIG. 13 illustrates another form ofelectrical valve which is applicableto the invention;

FIG. 14 illustrates a multiplier applicable to the invention;

FIG. 15 illustrates the functions which can be simulated with themultiplier of FIG. 14; and

FIG. 16 is a detailed illustration of the followup system for thetrimming lever and the throttle lever, respectively.

DESCRIPTION OF SPECIFIC EMBODIMENTS The following disclosure is offeredfor public dissemination in return for the grant ofa patent. Although itis detailed to ensure adequacy and aid understanding, this is notintended to prejudice that purpose ofa patent which is to cover each newinventive concept therein no matter how others may later disguise it byvariations in form or additions or further improvements. The claims atthe end hereof are intended as the chief aid toward this purpose, as itis these that meet the requirement of pointing out the parts,improvements, or combinations in which the inventive concepts are found.

In the arrangement according to FIG. 1, the air pressure p, and theengine speed n are supplied to a computer R. Therefrom the computer Rcalculates the setpoint value of the turbine gas temperature TGT Anactual value TGT of the turbine gas temperature is derived from theturbine by means of a sensor F. Setpoint value and actual value arecompared in a monitor. When a deviation occurs, either the lamp L1 orthe lamp L2 lights up depending upon whether the deviation is plus orminus. The trimming lever T which in turn influences the turbine gastemperature may be adjusted in dependence thereon. The monitor and thelights comprise a responsive means which could also include the actuatorA for automatically operating the lever T.

With the control principle according to FIG. 2, signals according to theair pressure p and speed n and an additional signal in response to theair temperature t are supplied to a computer R. From these the computerR calculates a setpoint value (a of the position of the trimming lever.The position of the trimming lever T is picked off by a sensor F whichsupplies an actual value (a for the position of the trimming lever. Thetwo values control a monitor which, when a deviation of actual value andsetpoint value occurs, causes a lamp L1 or L2 to light up, depending onthe sign of the deviation. Accordingly, the trimming lever T isadjusted. With the adjustment of the trimming lever T the turbine gastemperature (TGT) is influenced in an open circuit.

By way of example, the invention is applicable to the Rolls Royce engine-Tyne" MK 21 and MK 22, as it is described in the operating andmaintenance manual Tyne" MK 21/22 of MAN-Turbo, Munich.

Referring to FIG. 3, the turbine speed n is derived through an adapterelement 1 and processed in a computing element 2 in the form of afunction transmitter. A first signal proportion is developed at theoutput ofthe function transmitter 2, which represents the setpoint valueof the desired turbine gas temperature for the speed n of operation,however, without considering the altitude pressure. This value of theturbine gas temperature is corrected in a computing element 3 (actuallyan adding amplifier), in accordance with the altitude pressure. For thispurpose, a signal representative of the static pressure p, is derivedfrom a transmitter (already existing on the aircraft) through an adapterelement 4 and is applied to the adding amplifier 3.

A signal transmitter 5 is provided at which the static pressure can beestablished according to the altimeter reading. Through a switch 6 theone or the other pressure signals are alternatively applied to amplifier3. At the output ofthe adding amplifier 3, a signal w representing thesetpoint value of the desired turbine gas temperature is obtained forthe speed n (already established) and the static pressure p,,. Thissetpoint value of the turbine gas temperature may be indicated at adigital indicating device 7 for control purposes.

This setpoint value w of the turbine gas temperature is compared by asummation element 8 with a signal at representing the actual value ofthe turbine gas temperature which is derived from a measuring sensorthrough an adapter element 9. The error signal or the deviation actuatesthe electrical valves 11 and 12 through a summation element 10.Depending upon the direction of error, one or the other of blinkingdevices 13 or 14 is thereby actuated to cause the light connected to therespective blinking device to flash on and off. The human pilot carriesout a control movement with a trimming lever 16 until the blinkingsignal is extinguished. Therefore, he is in a position to adjust thetrimming lever into a position called for by the present flightconditions without computing operations and without having recourse to atable.

Since the engine responds to an adjustment ofthe trimming lever by atime constant, a gentle feedback" adapted to the time constant of theengine is provided. A transmitter 17 is connected with the trimminglever, which at the moment of adjustment of the trimming lever suppliesa signal Aa proportional to the angular adjustment to a summationelement 10 through an electrical valve 15, this signal being connectedin opposition to the deviation signal AT. If the angle signal from thetransmitter 17 corresponds to the magnitude required for compensatingthe deviation, then the output signal ofthc summation element 10 iszero. Therefore, the blinking ceases. If, however, the trimming lever isadjusted too far, then a counter signal is immediately supplied byactuation of the corresponding electrical valve 11 or 12.

With a fading of the deviation signals AT provision is made through anelectrical valve 15 for the signal across the summation element 10 tofade accordingly. With a correct adjustment of the trimming lever theoutput signal of the summation element 10 therefore continues to bezero.

Moreover, a followup circuit is provided which comprises an amplifier 18controlled by the angle signal Aa and a followup motor 19 by which thestator of the synchro 17 can be caused to follow the rotor connectedwith the trimming lever 16. This followup circuit has its time constantadapted to the time constant of the engine so that the synchro signal Aais weakened approximately with the time constant of the engine.

FIG. 4 illustrates the block circuit diagram of a control chain which isdesigned for the whole operating range. The design is similar to that ofFIG. 3, and like parts are referenced by the same reference numerals asin that Figure. However, the following differences exist:

Above a given speed and with different modes of operation an adjustmentof the trimming lever no longer has any influence on the turbine gastemperature. A switch 24 is provided for this purpose. From this switchsignals are derived for specific positions of trimming lever 16 andthrottle lever 23 which partly effect a changeover to another controlelement,

namely from control by the trimming lever 16 to control through thethrottle lever 23, and partly influence the computation of the setpointvalue of the turbine gas temperature in the computer. These are thefollowing switch signals:

Switch signal a suppresses the influence of the barometric pressure p,on the setpoint value of the turbine gas temperature determined in thecomputer.

Switch signal b preestablishes a setpoint value of the turbine gastemperature which is independent of the speed, thus is not derived fromthe speed but only from the position of the throttle lever.

Switch signal c is an angularly proportional feedback signalcorresponding to Act, which, however, indicates either the position ofthe trimming lever or the position of the throttle lever, depending onthe mode of operation. For the trimming lever 16 and the throttle lever23 one followup circuit each is provided which is formed of theamplifier l8 and the servomotor 19 in the case of the trimming leveraccording to FIG. 1. The position signal from the throttle lever issupplied by a transmitter 22. The stator of the transmitter can becaused to follow and adjustment of the throttle lever by a followupcircuit (loop) comprising the amplifier 20 and a servomotor 21. Thisfollowup cir- 'cuit operates with a time constant which is adapted tothe time constant of the engine.

Signal d effects the changeover of the blinking signals through signalgating devices and 26, respectively, from a pair of blinking lampsassociated with the trimming lever to a pair of blinking lampsassociated with the throttle lever, depending on which lever must beoperated to effect the correction of the turbine gas temperature in therespective mode of operation.

Another feature of the arrangement according to FIG. 4 is a multiplierelement 29 by which, from a specific speed on the coefficient with whichthe influence of the barometric pressure p, at the summing amplifier 3is taken into consideration, will be varied. This is done specificallyin the modes of operation takeoff" and highest cruising power".

FIG. 5 is an illustration similar to that of FIG. 3, however, with anarrangement in which the position of the trimming lever signal orrepresents the regulating variable in accordance with the manner of FIG.2. Like parts are referenced by the same reference numerals as in FIG.3. The computer includes an additional multiplier element 27 to which isapplied, on the one hand, the output of the adding amplifier 3 and, onthe other hand, a signal which is supplied by a sensor for the airtemperature t through an adapter element 28. The output of themultiplier element is indicative of the setpoint value a,,,,, for theposition of the trimming lever. The position of the trimming lever 16 ispicked off by a synchro 17 similar to FIG. 3. The output of the synchro17 is connected as an actual value across the summation element 8 inopposition to the setpoint value a The summation element controlsblinking devices 13 and 14, respectively, through electrical valves 11,12 in dependence on the sign of the difference a -'11 The blinkingdevices operate the respective lights to indicate if an adjustment ofthe trimming lever is required. Also with this arrangement, an automaticcontrol of the position of the trimming lever can be effected instead.

The electronic elements used with the arrangements of FIGS. 1 to 5 arecircuitries customary per se. For completion of the disclosure, a fewembodied forms of such circuitries used herein shall be describedhereinafter with reference to the FIGS. 6 to 16.

FIG. 6 shows an adapter element such as that referenced 1 and 4 in FIGS.3 to 5. Such an adapter element should have, on the one hand, a highinput resistance so that the load of the measured value transmitter islow. On the other hand, the measured value transmitter should beinfluenced only irrelevantly for safety reasons in case of short-circuitof the adapter element. The adapter element includes a high-amplifyingoperational amplifier 30 having one input to which the voltage U,; fromthe measured value transmitter (for instance n, p,,) is applied througha high resistor R For example, resistor R is I00 kiloohms. The outputvoltage U is connected in opposition across the other input FIG. 7illustrates schematically a function transmitter such as that referenced2 in FIG. 3. It copies an empirically determined function, for instanceone according to FIG. 8, by straight line portions; that is, the outputvoltage U, shall approximately depend on the input voltage U modifiedaccording to this function. Within the range of each straight lineportion, respectively, a linear relationship exists between U,, and UFor this purpose the input voltage U,; is applied to an operationalamplifier 34 through a resistor 32. From the output of the amplifier 34a negative feedback is effected through resistors 36, 38, 40. The ratioof the resulting resistance value of the resistors 36, 38, 40 to theresistance value of the resistor 32 first determines the effective gain,thus the ratio of U, and U The diodes 42, 44 in series with theresistors 38 and 40 respectively, are initially maintained conductive bya negative bias voltage of -15 volts applied through resistors 46, 48.With an increase in the input and output voltages U and U respectively,the diodes 44 and 42, respectively, are successively blocked, the pointin which this occurs being determined by the relative resistance of theresistors. Accordingly, there are changes in the effective negativefeedback resistor and the gain. Thus, the output voltage U, depends onthe input voltage U according to a broken line characteristic.

FIG. 9 illustrates an example of a computing element such as thatreferenced 3 in FIG. 3. It includes a summation element 50 and anoperational amplifier 52 having a gain A. The summation element adds upan input voltage U,., and the output voltage of the amplifier 52. Aninput voltage U is applied to amplifier 52 and its output voltage is A-UThus, at sum mation element 50 there is an output voltage:

FIG. 10 illustrates a summation amplifier as can be used, for example,for the element 8 in FIGS. 3 to 5. It includes a highamplifyingoperational amplifier S4 to the input of which two input voltages U, andU are applied through resistors R and R respectively. A negativefeedback is effected through a resistor R An output voltage is obtainedas follows:

The electrical valves 11 and 12 of FIG. 3 or 4 may be designed in themanner of FIG. 11. To a operational amplifier 56 an input voltage U, isapplied across an input Across the other input of the operationalamplifier 56 is applied a voltage which is derived from an adjustablepotentiometer 58 connected to a fixed DC voltage. The output of theoperational amplifier 56 is applied to the base of a transistor 62through a resistor 60. Depending on whether the input voltage U isgreater or smaller, when taken absolute, then the reference voltagederived from the potentiometer 53, the transistor 62 is controlledthrough or is blocked. The adjustable potentiometer 58 makes it possibleto adjust the threshold at which the electrical valve opens, thus (inFIG. 3) the dead range in which no correction signal is yet suppliedwith a deviation of actual value and command value.

The electrical valve 15 of FIG. 3 is of a different type and is actuallya multiplier element. It provides that a first input signal (forinstance, A01 in FIG. 3) has substantially the same waveform withrespect to time as does another signal AT. For this purpose, anoscillator 64 (FIG. 13) is provided which has a frequency controllableas a function of AT. The oscillator 64 controls choppers 66 and 68 forthe signal AT and for the signal Au, respectively. The chopped signalsare supplied to a summing element 10.

Thereby, pulses of constant width are supplied to the summation elementat a frequency dependent on AT. In the summing element 10, the choppedsignals are connected in opposition. As an output signal from thesumming element, the mean value of the resulting signal is used whichconsists of a pulse sequence of an amplitude (AT-A01) and a frequencydependent on AT. If AT approaches zero, the output signal alsoapproaches zero, since the pulse frequency decreases to zero, and thatis independently of the actual signal difference (AT-Aa). Of course, theoutput signal is also zero if AT Act. This circuit permits thecompensation of differences in the time course of the deviation AT andthe feedback of the trimming lever signal through the followup circuit17, 18, 19 (FIG. 3).

The multiplier 27 in FIG. 5 serves to form an expression for theproposition that:

the position of the trimming lever mt,,+b. It includes a summationelement 70 (FIG. 14) and an amplifier element 72. The summation elementhas applied thereto on the one hand the signal b and on the other handthe output of the amplifier element 72. The amplifier element 72amplifies-and thereby multiplies-the temperature signal applied theretoby a factor In, so that its output is M1 The output of the summationelement 70 supplies the above expression (ml,,+h) for the position ofthe trimming lever. Since b=f(p,,), the dependence of the output signala on t obvious from FIG. 15, results for different p,,.

The followup system of the trimming lever is shown in FIG. 16. The samearrangement would be employed for the followup system for the throttlelever A synchro 17 is connected to the trimming lever 16. The armatureof synchro 17 is rotatable with the trimming lever and is fed with aconstant voltage excitation. The stator of the synchro 17 is connectedwith the stator of a second synchro 17'. The armature of the synchro 17supplies the output signal Aa. This armature can be rotated to follow bythe output signal Aoz through an amplifier l8 and a time element 74through a servomotor 19.

I claim: 1. In an aircraft apparatus for use in controlling a propellerturbojet engine having a variable position throttle lever forestablishing an engine setting for a mode of operation of the aircraftand a variable position trimming lever for establishing an optimum valueof turbine gas temperature for the mode of operation and for selectedvariable factors which may include speed, air pressure, cruisingaltitude and air temperature, the improvement comprising:

sensor means responsive to the selected factors for producing inputsignals as a function of said selected factors;

computer means connected to said sensor means to respond to said inputsignals for producing a trimming lever setpoint signal indicative ofsaid optimum value of turbine gas temperature;

additional sensor means connected to the engine for producing an actualsetting signal which is a function of the actual setting of the trimminglever; and

responsive means connected to said additional sensor means and to saidcomputer means for producing a response indicative of the direction ofdeviation of the deviation, if any, between the actual setting signaland the setpoint signal.

2. In an apparatus as set forth in claim 1, wherein said computer meanscomprises:

function transmitter means connected to receive one of said inputsignals for modifying said one input signal according to a predeterminedfunction to produce a modified input signal; and

adding amplifier means for producing said setpoint signal as a functionof said modified input signal and the other of the input signals.

3. In an apparatus as set forth in claim 2, wherein the sensor meansproducing said one input signal is responsive to engine speed and thesensor means producing said other signal is responsive to air pressure.

4. In an apparatus as set forth in claim 3, wherein said computer meanscomprises multiplier means effective at speeds in excess of apredetermined value for changing the effect of said other signal in saidadding amplifier means.

5. In an apparatus as set forth in claim 4 including switch meansconnected to the throttle lever and to the amplifier means forsuppressing the effect of said other signal when the throttle lever isinapredetermined range. I

6. In an apparatus as set forth in claim 5, wherein the responsive meansproduces an error signal as a function of the magnitude of deviation andincluding means connected to the trimming lever for producing a gentlefeedback signal of the displacement of the trimming lever and connectedto the responsive means for applying said feedback signal in oppositionto the error signal.

7. In an apparatus as set forth in claim 6, wherein said responsivemeans includes two visual indicators, one indicator becoming effectivewhen the deviation is of one sign and the other becoming effective whenthe deviation is ofthe opposite sign.

8. In an apparatus as set forth in claim 6, wherein said responsivemeans is connected to said trimming lever to automatically adjust thelatter to eliminate the deviation, if any.

9. In an apparatus as set forth in claim 2, wherein said computercomprises multiplier means effective at speeds in excess of apredetermined value for changing the effect of said other signal in saidadding amplifier means.

10. In an apparatus as set forth in claim 2,

wherein a sensor means is responsive to air temperature for producing atemperature responsive signal;

said computer apparatus including multiplier means connected to said airtemperature responsive sensor means for multiplying the output of theadding amplifier means with said temperature responsive signal toproduce said setpoint signal.

11. In an apparatus as set forth in claim 1, including control meansconnected to said throttle and said computer means for producing, inresponse to engine speeds above a given value, an output setpoint signalfrom said computer means which is a function only of the throttle leversetting.

12. In an apparatus as set forth in claim 11, wherein the responsivemeans produces an error signal as a function of the magnitude ofdeviation and including means connected to the throttle lever forproducing a gentle feedback signal ofthe displacement of the throttlelever and connected to the responsive means for applying said feedbacksignal in opposition to the error signal.

13. In an apparatus as set forth in claim 1, wherein said additionalsensor means is responsive to the turbine gas temperature ofthe engine.

14. In an apparatus as set forth in claim 1, wherein said additionalsensor means is connected to the trimming lever to be directly affectedby the position of the trimming lever.

1. In an aircraft apparatus for use in controlling a propeller turbojetengine having a variable position throttle lever for establishing anengine setting for a mode of operation of the aircraft and a variableposition trimming lever for establishing an optimum value of turbine gastemperature for the mode of operation and for selected variable factorswhich may include speed, air pressure, cruising altitude and airtemperature, the improvement comprising: sensor means responsive to theselected factors for producing input signals as a function of saidselected factors; computer means connected to said sensor means torespond to said input signals for producing a trimming lever setpointsignal indicative of said optimum value of turbine gas temperature;additional sensor means connected to the engine for producing an actualsetting signal which is a function of the actual setting of the trimminglever; and responsive means connected to said additional sensor meansand to said computer means for producing a response indicative of thedirection of deviation of the deviation, if any, between the actualsetting signal and the setpoint signal.
 2. In an apparatus as set forthin claim 1, wherein said computer means comprises: function transmittermeans connected to receive one of said input signals for modifying saidone input signal according to a predetermined function to produce amodified input signal; and adding amplifier means for producing saidsetpoint signal as a function of said modified input signal and theother of the input signals.
 3. In an apparatus as set forth in claim 2,wherein the sensor means producing said one input signal is responsiveto engine speed and the sensor means producing said other signal isresponsive to air pressure.
 4. In an apparatus as set forth in claim 3,wherein said computer means comprises multiplier means effective atspeeds in excess of a predetermined value for changing the effect ofsaid other signal in said adding amplifier means.
 5. In an apparatus asset forth in claim 4 including switch means connected to the throttlelever and to the amplifier means for suppressing the effect of saidother signal when the throttle lever is in a predetermined range.
 6. Inan apparatus as set forth in claim 5, wherein the responsive meansproduces an error signal as a function of the magnitude of deviation andincluding means connected to the trimming lever for producing a gentlefeedback signal of the displacement of the trimming lever and connectedto the responsive means for applying said feedback signal in oppositionto the error signal.
 7. IN an apparatus as set forth in claim 6, whereinsaid responsive means includes two visual indicators, one indicatorbecoming effective when the deviation is of one sign and the otherbecoming effective when the deviation is of the opposite sign.
 8. In anapparatus as set forth in claim 6, wherein said responsive means isconnected to said trimming lever to automatically adjust the latter toeliminate the deviation, if any.
 9. In an apparatus as set forth inclaim 2, wherein said computer comprises multiplier means effective atspeeds in excess of a predetermined value for changing the effect ofsaid other signal in said adding amplifier means.
 10. In an apparatus asset forth in claim 2, wherein a sensor means is responsive to airtemperature for producing a temperature responsive signal; said computerapparatus including multiplier means connected to said air temperatureresponsive sensor means for multiplying the output of the addingamplifier means with said temperature responsive signal to produce saidsetpoint signal.
 11. In an apparatus as set forth in claim 1, includingcontrol means connected to said throttle and said computer means forproducing, in response to engine speeds above a given value, an outputsetpoint signal from said computer means which is a function only of thethrottle lever setting.
 12. In an apparatus as set forth in claim 11,wherein the responsive means produces an error signal as a function ofthe magnitude of deviation and including means connected to the throttlelever for producing a gentle feedback signal of the displacement of thethrottle lever and connected to the responsive means for applying saidfeedback signal in opposition to the error signal.
 13. In an apparatusas set forth in claim 1, wherein said additional sensor means isresponsive to the turbine gas temperature of the engine.
 14. In anapparatus as set forth in claim 1, wherein said additional sensor meansis connected to the trimming lever to be directly affected by theposition of the trimming lever.